Java 如何通过图像的 Base64 编码字符串识别文件类型
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How to identify file type by Base64 encoded string of a image
提问by dinesh707
采纳答案by Half Ass Dev
I have solved my problem with using mimeType = URLConnection.guessContentTypeFromStream(inputstream);
我已经解决了我使用的问题 mimeType = URLConnection.guessContentTypeFromStream(inputstream);
{ //Decode the Base64 encoded string into byte array
// tokenize the data since the 64 encoded data look like this "data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAoAAAAKAC"
String delims="[,]";
String[] parts = base64ImageString.split(delims);
String imageString = parts[1];
byte[] imageByteArray = Base64.decode(imageString );
InputStream is = new ByteArrayInputStream(imageByteArray);
//Find out image type
String mimeType = null;
String fileExtension = null;
try {
mimeType = URLConnection.guessContentTypeFromStream(is); //mimeType is something like "image/jpeg"
String delimiter="[/]";
String[] tokens = mimeType.split(delimiter);
fileExtension = tokens[1];
} catch (IOException ioException){
}
}
回答by naXa
This code is using regex pattern to extract mime type from Base64 string. Though it's written in JavaScript, you can try to implement the same thing in Java.
此代码使用正则表达式模式从 Base64 字符串中提取 MIME 类型。尽管它是用 JavaScript 编写的，但您可以尝试用 Java 实现相同的功能。
function base64Mime(encoded) {
var result = null;
if (typeof encoded !== 'string') {
return result;
}
var mime = encoded.match(/data:([a-zA-Z0-9]+\/[a-zA-Z0-9-.+]+).*,.*/);
if (mime && mime.length) {
result = mime[1];
}
return result;
}
Usage:
用法：
var encoded = 'data:image/png;base64,iVBORw0KGgoAA...5CYII=';
console.log(base64Mime(encoded)); // "image/png"
console.log(base64Mime('garbage')); // null
Source: miguelmota/base64mime (GitHub)
回答by fatih bayhan
I did just this: (file is my base64 string)
我就是这样做的：（文件是我的 base64 字符串）
int extentionStartIndex = file.indexOf('/');
int extensionEndIndex = file.indexOf(';');
int filetypeStartIndex = file.indexOf(':');
String fileType = file.substring(filetypeStartIndex + 1, extentionStartIndex);
String fileExtension = file.substring(extentionStartIndex + 1, extensionEndIndex);
System.out.println("fileType : " + fileType);
System.out.println("file Extension :" + fileExtension);
回答by naXa
/**
* Extract the MIME type from a base64 string
* @param encoded Base64 string
* @return MIME type string
*/
private static String extractMimeType(final String encoded) {
final Pattern mime = Pattern.compile("^data:([a-zA-Z0-9]+/[a-zA-Z0-9]+).*,.*");
final Matcher matcher = mime.matcher(encoded);
if (!matcher.find())
return "";
return matcher.group(1).toLowerCase();
}
Usage:
用法：
final String encoded = "data:image/png;base64,iVBORw0KGgoAA...5CYII=";
extractMimeType(encoded); // "image/png"
extractMimeType("garbage"); // ""
回答by Muhammad Tahir
if you want to get Mime type use this one
如果你想获得 Mime 类型，请使用这个
const body = {profilepic:"data:image/png;base64,abcdefghijklmnopqrstuvwxyz0123456789"};
let mimeType = body.profilepic.match(/[^:]\w+\/[\w-+\d.]+(?=;|,)/)[0];
===========================================
if you want to get only type of it like (png, jpg) etc
============================================
如果您只想获取类型它像（png，jpg）等
const body2 = {profilepic:"data:image/png;base64,abcdefghijklmnopqrstuvwxyz0123456789"};
let mimeType2 = body2.profilepic.match(/[^:/]\w+(?=;|,)/)[0];
回答by Suman
You can check like this:
你可以这样检查：
String[] strings = base64String.split(",");
String extension;
switch (strings[0]) {//check image's extension
case "data:image/jpeg;base64":
extension = "jpeg";
break;
case "data:image/png;base64":
extension = "png";
break;
default://should write cases for more images types
extension = "jpg";
break;
}
